Recently, various types of controls containing the control of converting sensor signals output from various kinds of sensors for detecting physical quantities such as temperature, pressure, magnetic field, etc. to digital data and controlling the driving of an engine by using the digital data, etc. have been carried out in vehicles, for example. With respect to these sensors, they have normally parameters dependent on the temperature such as offset and sensitivity, and thus there occurs a disadvantage that the above sensor signals indicate different values in accordance with the temperature at that time although the detection target physical quantity is identical. When the difference between the actual physical quantity and the sensor signal is increased due to the characteristic of the sensor as described above, the reliability of the control itself described above is greatly lowered. Therefore, some correction has been hitherto carried out on the sensor signal in consideration of the temperature characteristic of the sensor as described above. A method using a sensor device described in JP-A-11-44585 (Patent Document 1) is known as an example of the correcting method.
That is, according to this sensor device, the relationship between the variation of the actual physical quantity and the sensor signal is approximately linearly, that is, by a linear expression in consideration of the offset and the sensitivity to determine a correcting coefficient for correcting the signal output from the sensor to a value which considers the temperature of the sensor at that time. The correcting coefficient thus determined is suitably stored, and when a physical quantity is detected, the temperature of the sensor is determined, and the physical quantity detected on a case-by-case basis (the real-time detected physical quantity) is corrected by using the temperature-correcting coefficient considering the sensor temperature thus determined.
With respect to some sensor devices, the parameters such as the offset, the sensitivity, etc. vary non-linearly dependently on the temperature in many cases. In this case, the variation of the sensor signal with respect to the actual variation of the physical quantity is more complicated due to the non-linear temperature characteristics of these parameters. In addition, in the conventional sensor device described above, the relationship between the physical quantity to be detected and the sensor signal is linearly approximated in consideration of the offset, the sensitivity, etc. Therefore, when the sensor device is applied to a sensor in which the above-described parameters themselves have non-linear temperature characteristics such as an infrared sensor using a thermopile, a magnetic sensor using a magneto-resistance sensor, a current sensor or the like, the detection precision is unavoidably lowered.